<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			#main{
				width: 300px;
				height: 100px;
				border: 1px solid red;
				display:flex;
				justify-content: center;
				align-items: center;
			}
			#main div{
				flex-basis: 20%;
				height: 60px;
			}
			
			
		</style>
	</head>
	<body>
		<div id="main">
			<div style="background:red">a</div>
			<div style="background: green">b</div>
			<div style="background:blue">c</div>
		</div>
	</body>
</html>
